Method of making circuit board module

ABSTRACT

A circuit board module includes a circuit board and a heat-dissipating device. The circuit board includes a ceramic substrate, and a circuit pattern formed on a surface of the ceramic substrate. The circuit board is sinter-bonded to a main body of the heat-dissipating device. A method of making the circuit board module is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 12/800,414, filed May 13, 2010 (now U.S. Pat. No. 8,549,739), whichclaims priority to Taiwanese Application No. 098116189, filed May 15,2009 (now Patent No. 201041496), the full disclosures of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a circuit board module, more particularly to acircuit board module capable of dissipating heat and to a method ofmaking the same.

2. Description of the Related Art

Generally, a conventional high-power electronic element, such as ahigh-brightness light emitting diode (LED), a concentrator photovoltaiccell, or an insulated gate bipolar transistor (IGBT), generates a greatamount of heat when being operated. The high-power electronic elementmay be damaged when the heat generated by the same is unable to beproperly dissipated, thereby requiring a heat sink for rapid heatdissipation.

Referring to FIG. 1, a conventional circuit board module includes acircuit board 92 and a heat sink 94, and is adapted for supporting anelectronic element 91 and dissipating heat from the same. The electronicelement 91 is first disposed on the circuit board 92, and the circuitboard 92 is subsequently connected to a main body 941 of the heat sink94 using a thermally conductive adhesive 93 or solder (not shown). Heatproduced by the electronic element 91 can be transferred to a pluralityof fins 942 of the heat sink 94 through the main body 941 of the heatsink 94, and hence can be rapidly dissipated.

However, thermal resistance of the thermally conductive adhesive 93 (orsolder) may influence heat-dissipation efficiency for the electronicelement 91. Reduction in the thermal resistance between the electronicelement 91 and the heat sink 94 is hence necessary so as to enhanceheat-dissipation efficiency. Furthermore, the thermally conductiveadhesive 93 (or solder) may rapidly age and degrade in ahigh-temperature environment such that bonding between the circuit board92 and the main body 941 of the heat sink 94 may be adversely affected.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a circuitboard module that can overcome the aforesaid drawbacks of the prior art,and a method of making the same.

According to one aspect of this invention, there is provided a method ofmaking a circuit board module suitable for supporting and dissipatingheat from an electronic element. The method comprises: providing aceramic-copper plate that includes a ceramic substrate and two copperlayers formed on two opposite surfaces of the ceramic substrate;patterning one of the copper layers so as to form a copper pattern;providing a heat-dissipating device; providing a positioning unit on amain body of the heat-dissipating device and on the other one of thecopper layers; retaining the ceramic-copper plate on the main body ofthe heat-dissipating device relative to each other through the use ofthe positioning unit such that the ceramic-copper plate is in contactwith the main body of the heat-dissipating device; and conducting a heattreatment so as to bond the ceramic-copper plate to the main body of theheat-dissipating device.

According to another aspect of this invention, there is provided amethod of making a circuit board module suitable for supporting anddissipating heat from an electronic element. The method comprises:providing a ceramic-copper plate that includes a ceramic substrate andtwo copper layers formed on two opposite surfaces of the ceramicsubstrate; patterning one of the copper layers so as to form a copperpattern; providing a heat-dissipating device; providing an intermediatecopper plate; providing a positioning unit on a main body of theheat-dissipating device, the other one of the copper layers, and theintermediate copper plate; retaining the intermediate copper platebetween the ceramic-copper plate and the main body of theheat-dissipating device through the use of the positioning unit; andconducting a heat treatment so as to bond the intermediate copper plateto the ceramic-copper plate and the main body of the heat-dissipatingdevice.

According to yet another aspect of this invention, there is provided acircuit board module adapted for supporting and dissipating heat from anelectronic element. The circuit board module includes a circuit board, aheat-dissipating device, and an intermediate copper plate. The circuitboard includes a ceramic substrate, and a circuit layer that has acircuit pattern and that is formed on a surface of the ceramicsubstrate. The heat-dissipating device includes a main body. Theintermediate copper plate is disposed between and sinter-bonded to thecircuit board and the main body of the heat-dissipating device.

According to still another aspect of this invention, there is provided acircuit board module adapted for supporting and dissipating heat from anelectronic element. The circuit board module includes a circuit boardand a heat-dissipating device. The circuit board includes a ceramicsubstrate, and a circuit pattern that is formed on a surface of theceramic substrate. The heat-dissipating device includes a main body. Thecircuit board is sinter-bonded to the main body of the heat-dissipatingdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiments of this invention, with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic view to illustrate a conventional circuit boardmodule that is used for an electronic element;

FIGS. 2( a), 2(b), and 2(c) show consecutive steps of making a circuitboard of the first preferred embodiment of a circuit board moduleaccording to the present invention;

FIG. 3 is a schematic view to illustrate a heat-dissipating device ofthe first preferred embodiment of the circuit board module;

FIG. 4 is a schematic view to illustrate the first preferred embodimentof the circuit board module;

FIGS. 5( a), 5(b), and 5(c) show consecutive steps of making a circuitboard of the second preferred embodiment of a circuit board moduleaccording to the present invention;

FIG. 6 is a schematic view to illustrate an intermediate copper plate ofthe second preferred embodiment of the circuit board module;

FIG. 7 is a schematic view to illustrate the second preferred embodimentof the circuit board module;

FIG. 8 is a schematic view to illustrate a heat-dissipating device ofthe third preferred embodiment of a circuit board module according tothe present invention;

FIG. 9 is a schematic view to illustrate an intermediate copper plate ofthe third preferred embodiment of the circuit board module;

FIG. 10 is a schematic view to illustrate a plurality of pillars of thethird preferred embodiment of the circuit board module, which are usedto secure the intermediate copper plate shown in FIG. 9 and theheat-dissipating device shown in FIG. 8; and

FIG. 11 is a schematic view to illustrate the third preferred embodimentof the circuit board module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it shouldbe noted that the same reference numerals have been used to denote likeelements throughout the specification.

The first preferred embodiment of a method of making a circuit boardmodule suitable for supporting and dissipating heat from an electronicelement is described as follows.

Referring to FIG. 2( a), a ceramic-copper plate 1 is provided, andincludes a ceramic substrate 11 and two copper layers 12,13 that areformed on two opposite surfaces of the ceramic substrate 11. The copperlayers 12,13 are sinter-bonded to the ceramic substrate 11 using directcopper bonding (DCB). The ceramic-copper plate 1 is commerciallyavailable in the market.

Referring to FIGS. 2( b) and 2(c), the copper layer is patterned so asto form a copper pattern 12′ (i.e., a circuit pattern), and the copperlayer 13 is patterned so as to form a plurality of first positioningelements 14, thereby forming the circuit board 10. The circuit board 10shown in FIG. 2( c) is a reverse view of the circuit board 10 shown inFIG. 2( b). The copper layers 12,13 may be patterned through a processfrequently used for making a printed circuit board (PCB), such as aphotolithography process using a photoresist or a lithography processusing printing ink, followed by etching. In this embodiment, the firstpositioning elements 14 are formed as indentations.

Referring to FIG. 3, a heat-dissipating device 2 is provided, andincludes a main body 21 and a plurality of fins 22 that protrude fromthe main body 21. A plurality of second positioning elements 23 areformed on the main body 21, and correspond in position to the respectivefirst positioning elements 14 (see FIG. 2( c)). In this embodiment, thesecond positioning elements 23 are formed as protrusions so as torespectively engage the first positioning elements 14 (i.e., theindentations, see FIG. 2( c)). A cross-section of the protrusionsconforms to that of the indentations, and may be circular, square,triangular, etc. A thickness of the protrusions is not larger than adepth of the indentations. Preferably, the thickness of the protrusionsis slightly smaller than the depth of the indentations. In thisembodiment, the main body 21 and the fins 22 of the heat-dissipatingdevice 2 are made of copper. It should be noted that other types ofheat-dissipating devices (e.g., a water-cooled heat-dissipating deviceand a ceramic heat-dissipating device) are suitable to make the circuitboard module of this invention as long as the second positioningelements 23 could be formed thereon.

Referring to FIG. 4, the circuit board 10 is retained on the main body21 of the heat-dissipating device 2 relative to each other through thefirst and second positioning elements 14,23 such that the circuit board10 is in contact with the main body 21 of the heat-dissipating device 2.Since the thickness of the protrusions is not larger than the depth ofthe indentations, a surface of the copper layer 13 of the circuit board10 is able to contact a surface of the main body 21. At least one of theaforementioned surface of the copper layer 13 and the aforementionedsurface of the main body 21 is copper oxide. The assembly of the circuitboard 10 and the heat-dissipating device 2 is placed in a furnace havingoxygen content less than 10 ppm, and is subjected to a heat treatmentusing DCB at a temperature that is lower than the melting point ofcopper (about 1083° C.) and higher than the eutectic temperature of thecopper-copper oxide eutectic (1063° C.). The copper layer 13 of thecircuit board 10 is sinter-bonded (or eutectic-bonded) to the main body21, and the circuit board 10 is hence well secured to the main body 21.Accordingly, the first preferred embodiment of a circuit board module100 according to the present invention is formed, and the circuit board10 thereof is adapted for supporting an electronic element (not shown).

It should be noted that the first positioning elements 14 may be formedas protrusions (see FIG. 5(C)), and the second positioning elements 23may be formed as indentations (see FIG. 8) so as to engage the firstpositioning elements 14 in other embodiments. If the first and secondpositioning elements 14,23 are respectively protrusions andindentations, a surface of the ceramic substrate 11 is sinter-bonded toa surface of the main body 21 of the heat-dissipating device 2.Furthermore, it should be noted that the first and second positioningelements 14,23 may be both formed as indentations in other embodiments.If the first and second positioning elements 14,23 are both formed asindentations, a plurality of pillars (not shown in the figures of thisembodiment) are required so that each of the pillars is insertedfittingly in a respective one of the first positioning elements 14 and arespective one of the second positioning elements 23.

In this embodiment, if the main body 21 of the heat-dissipating device 2is made from a ceramic material, the first positioning elements 14 arepreferably formed as indentations. Examples of the ceramic materialsuitable for the main body 21 of the heat-dissipating device 2 includeAl₂O₃, AlN, TiO₂, SiO₂, ZrO₂, ZnO, 2MgO.SiO₂, and BaTiO₃. Preferably,the main body 21 of the heat-dissipating device 2 is made from Al₂O₃ orAlN.

According to the present invention, the second preferred embodiment ofthe method is described as follows. Referring to FIGS. 5( a)-5(c), thesteps of making the circuit board 10′ are similar to the steps of makingthe circuit board 10 shown in FIG. 2( c) except that the firstpositioning elements 14′ are formed as protrusions. The circuit board10′ shown in FIG. 5( c) is a reverse view of the circuit board 10′ shownin FIG. 5( b). The heat-dissipating device 2′ shown in FIG. 7 isprovided, and the second positioning elements 23 formed on the main body21′ of the heat-dissipating device 2′ have a structure identical to thatof the second positioning elements 23 shown in FIG. 3, i.e.,protrusions. Namely, the configuration of the heat-dissipating device 2′shown in FIG. 7 is the same as that of the heat-dissipating device 2shown in FIG. 3. In this embodiment, the heat-dissipating device 2′ ismade of a ceramic material (preferably aluminum oxide), and the firstpositioning elements 14′ (see FIG. 5( c)) and the second positioningelements 23 (see FIG. 3) are staggered.

Referring to FIG. 6, an intermediate copper plate is provided. Aplurality of through-holes 31,32 are formed in the intermediate copperplate 3. Each of the through-holes 31 corresponds in position to andaccommodates a respective one of the first positioning elements 14′, andeach of the through-holes 32 corresponds in position to and accommodatesa respective one of the second positioning elements 23.

Referring to FIG. 7, the intermediate copper plate is retained betweenthe circuit board 10′ and the main body 21′ of the heat-dissipatingdevice 2′ through the first positioning elements 14′ and the secondpositioning elements 23. The steps of retaining the intermediate copperplate 3 between the circuit board 10′ and the main body 21′ aredescribed as follows. First, the intermediate copper plate 3 is stackedon the main body 21′ so that the second positioning elements 23 engagethe through-holes 32. Afterward, the circuit board 10′ is stacked on theintermediate copper plate 3 so that the first positioning elements 14′engage the through-holes 31.

Thicknesses of the first and second positioning elements 14′,23 are notlarger than depths of the through-holes 31,32 (i.e., a thickness of theintermediate copper plate 3). Thus, two opposite surfaces of theintermediate copper plate 3 are able to respectively contact a surfaceof the main body 21′ and a surface of the ceramic substrate 11 of thecircuit board 10′. Preferably, the thickness of the intermediate copperplate 3 is slightly larger than the thicknesses of the first and secondpositioning elements 14′,23. The aforementioned two opposite surfaces ofthe intermediate copper plate 3 are copper oxide. After retaining theintermediate copper plate 3 between the circuit board 10′ and theheat-dissipating device 2′, the heat treatment as mentioned in the firstpreferred embodiment of the method is conducted so as to sinter-bond theintermediate copper plate 3 to the circuit board 10′ and the main body21′ of the heat-dissipating device 2′. Consequently, the secondpreferred embodiment of the circuit board module 100′ according to thepresent invention is made.

In this embodiment, the intermediate copper plate 3 has an area which isequal to that of the main body 21′. The intermediate copper plate 3 iscapable of rapidly transferring heat in a horizontal direction (i.e.,X-Y direction), thereby being able to quickly transfer heat from anelectronic element to all surfaces of the main body 21′. Subsequently,the main body 21′ can vertically transfer the heat to the fins 22′, andthe fins 22′ are able to dissipate the heat.

According to the present invention, the third preferred embodiment ofthe method is described as follows. The steps of making the circuitboard 10 (see FIG. 11) in this embodiment of the method are the same asthe steps of making the circuit board 10 (see FIG. 2( c)) in the firstpreferred embodiment of the method. Therefore, the first positioningelements 14 are formed as first indentations. Referring to FIG. 8, theheat-dissipating device 2″ is provided. The second positioning elements23″ are formed as second indentations on the main body 21″ of theheat-dissipating device 2″. Referring to FIG. 9, the intermediate copperplate 3′ is provided, and the through-holes 33′ are formed therein. Eachof the through-holes 33′ corresponds in position to a respective one ofthe first indentations and a respective one of the second indentations.Referring to FIG. 10, a plurality of pillars 4 are provided. Each of thepillars 4 is inserted fittingly into the respective one of the firstindentations, the respective one of the second indentations, and therespective one of the through-holes 33′. In this embodiment, the pillars4 are made of copper. It should be noted that the pillars might be madeof ceramic in other embodiments. The heat-dissipating device 2″ in thisembodiment is made of a ceramic material (preferably aluminum oxide).

Referring to FIG. 11, the intermediate copper plate 3′ is retainedbetween the circuit board 10 and the main body 21″ of theheat-dissipating device 2″. The steps of retaining the intermediatecopper plate 3′ between the circuit board 10 and the main body 21″ areas follows. First, the intermediate copper plate 3′ is stacked on themain body 21″ so that each of the through-holes 33′ is registered withthe respective one of the second indentations (see FIG. 10). Each of thepillars 4 is inserted into a respective pair of the through holes 33′and the second indentations (see FIG. 10). Afterward, the circuit board10 is stacked on the intermediate copper plate 3′ so that the remainingpart of each of the pillars 4 is inserted into the respective one of thefirst indentations. Two opposite surfaces of the intermediate copperplate 3′ are able to respectively contact the copper layer 13 of thecircuit board 10 and the main body 21″ of the heat-dissipating device2″. The heat treatment as mentioned in the first preferred embodiment ofthe method is conducted so as to sinter-bond the intermediate copperplate 3′ to the circuit board 10 and the main body 21′ of theheat-dissipating device 2″. Therefore, the third preferred embodiment ofthe circuit board module 100″ according to the present invention ismade. The intermediate copper plate 3′ of the third preferred embodimentof the circuit board module 100″ is also able to rapidly transfer heatin the horizontal direction like the intermediate copper plate 3 of thesecond preferred embodiment of the circuit board module 100′ (see FIG.7).

It should be noted that the second and third preferred embodiments ofthe method are preferably applied to make a circuit board module havinga ceramic heat-dissipating device since the disadvantage of the ceramicmaterial of the heat-dissipating device, i.e., poor heat conduction in ahorizontal direction, can be compensated by an intermediate copperplate.

By virtue of the first positioning elements 14,14′, the secondpositioning elements 23,23″, the pillars 4, and the through-holes31,32,33′ of the intermediate copper plate 3,3′, the circuit board10,10′ can be securely maintained on the main body 21,21′,21″ during theheat treatment, thereby increasing the production yield.

The ceramic substrate 11 of the circuit board module 100,100′,100″serves as an electrical insulating layer, and is well secured to themain body 21,21′,21″ via sinter-bonding. Since no thermally conductiveadhesives and solder is used, thermal resistance between an electronicelement and the heat-dissipating device 2,2′,2″ is avoided. Thus, thecircuit board module 100,100′,100″ of this invention has betterheat-dissipation efficiency compared to the conventional circuit boardmodule shown in FIG. 1.

While the present invention has been described in connection with whatare considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation andequivalent arrangements.

What is claimed is:
 1. A method of making a circuit board modulesuitable for supporting and dissipating heat from an electronic element,comprising: providing a ceramic-copper plate that includes a ceramicsubstrate and two copper layers formed on two opposite surfaces of theceramic substrate; patterning one of the copper layers so as to form acopper pattern; providing a heat-dissipating device; providing apositioning unit on a main body of the heat-dissipating device and onthe other one of the copper layers; retaining the ceramic-copper plateon the main body of the heat-dissipating device relative to each otherthrough the use of the positioning unit such that the ceramic-copperplate is in contact with the main body of the heat-dissipating device;and conducting a heat treatment so as to bond the ceramic-copper plateto the main body of the heat-dissipating device, wherein the positioningunit includes first positioning elements formed on the other one of thecopper layers, and second positioning elements respectively engaging thefirst positioning elements and formed on the main body of theheat-dissipating device, one of a pair of the first and secondpositioning elements which engage each other being formed as anindentation, the other one of the pair of the first and secondpositioning elements being formed as a protrusion.
 2. The method ofclaim 1, wherein the first positioning elements are formed asindentations, the second positioning elements being formed asprotrusions.
 3. The method of claim 2, wherein the main body and thesecond positioning elements of the heat-dissipating device are formedtogether by molding.
 4. The method of claim 1, wherein the main body ofthe heat-dissipating device is made of copper.
 5. The method of claim 1,wherein the second positioning elements of the heat-dissipating deviceare formed on the main body of the heat-dissipating device, which ispreformed.